2
Modeling for Endangered-Species
Recovery: Gray Wolves in the
Western Great Lakes Region
Jean Fitts Cochrane, Robert G. Haight, and
Anthony M. Starfield
23
2.1 Introduction
The Federal Endangered Species Act is intended to conserve endangered
and threatened species and their habitats and to improve the species’ status
so that they no longer need protection under the Act. In the process of
planning the recovery of threatened or endangered species, the U.S.
Fish and Wildlife Service increasingly uses demographic models to predict
population growth and risk of extinction, investigate the factors responsible for species endangerment, and examine the relative effectiveness
of alternative management options for species recovery. Demographic
models range from simple matrix models for estimating population change
(Getz and Haight 1989) to complex, spatially explicit, individual-based
models of population dynamics (Dunning et al. 1995). Such models require
at a minimum an understanding of the age, stage, and social structure of the
population and estimates of reproductive success and survivorship for
different life stages. The purpose of this chapter is to describe an example
of the construction of a demographic model with application to questions
associated with the recovery and management of the endangered gray
wolf (Canis lupus)population in the western Great Lakes region of the
United States.
The most common use of demographic models in recovery planning is
the prediction of long-term, range-wide extinction risks, a process called
population viability analysis (PVA) [see Boyce (1992a) and Beissinger and
Westphal (1998) for review]. An endangered-species recovery plan contains
criteria for recovery (i.e., delisting) and reclassification (i.e., change from
endangered to threatened status) that specify goals for the size, distribution, and other attributes of the population. The results of a PVA inform
recovery planners who set the population goals. For example, Kelly et al.
(1999) and Ellis et al. (1999) describe applications of commercial PVA
software in recovery planning for the endangered red wolf (Canis rufus)
and Florida panther (Felis concolor coryi) in the southern United States. In
other cases, such as the endangered piping plover (Charadrius melodus)
Modeling for Endangered-Species
Recovery: Gray Wolves in the
Western Great Lakes Region
Jean Fitts Cochrane, Robert G. Haight, and
Anthony M. Starfield
23
2.1 Introduction
The Federal Endangered Species Act is intended to conserve endangered
and threatened species and their habitats and to improve the species’ status
so that they no longer need protection under the Act. In the process of
planning the recovery of threatened or endangered species, the U.S.
Fish and Wildlife Service increasingly uses demographic models to predict
population growth and risk of extinction, investigate the factors responsible for species endangerment, and examine the relative effectiveness
of alternative management options for species recovery. Demographic
models range from simple matrix models for estimating population change
(Getz and Haight 1989) to complex, spatially explicit, individual-based
models of population dynamics (Dunning et al. 1995). Such models require
at a minimum an understanding of the age, stage, and social structure of the
population and estimates of reproductive success and survivorship for
different life stages. The purpose of this chapter is to describe an example
of the construction of a demographic model with application to questions
associated with the recovery and management of the endangered gray
wolf (Canis lupus)population in the western Great Lakes region of the
United States.
The most common use of demographic models in recovery planning is
the prediction of long-term, range-wide extinction risks, a process called
population viability analysis (PVA) [see Boyce (1992a) and Beissinger and
Westphal (1998) for review]. An endangered-species recovery plan contains
criteria for recovery (i.e., delisting) and reclassification (i.e., change from
endangered to threatened status) that specify goals for the size, distribution, and other attributes of the population. The results of a PVA inform
recovery planners who set the population goals. For example, Kelly et al.
(1999) and Ellis et al. (1999) describe applications of commercial PVA
software in recovery planning for the endangered red wolf (Canis rufus)
and Florida panther (Felis concolor coryi) in the southern United States. In
other cases, such as the endangered piping plover (Charadrius melodus)